Infection with toxigenic and atoxigenic strains of Aspergillus flavus induces different transcriptional signatures in maize kernels

Abstract

The application of atoxigenic Aspergillus flavus strains in maize fields has been shown to be an effective strategy for controlling contamination of aflatoxins, potent carcinogens produced by the fungus. This study monitored the expression levels of 18 defense genes against toxigenic and atoxigenic A. flavus strains in developing maize kernels over a time course of 96 h after inoculation. A stronger upregulation of genes encoding pathogenesis-related proteins, oxidative stress-related proteins, transcriptional factors and lipoxygenases were observed in response to the atoxigenic strain. On the other side, this strain showed a significant enhanced growth in the later stages of infection, measured as copy number of the constitutive calmodulin gene. These results suggest that overexpression of maize-defense-associated genes observed in response to the atoxigenic strain could contribute to an aflatoxin reduction. The identification of genes significantly affecting the resistance to A. flavus or aflatoxin accumulation would accelerate the development of resistant cultivars. ARTICLE HISTORY

Fusarium verticillioides and Aspergillus flavus Co-Occurrence Influences Plant and Fungal Transcriptional Profiles in Maize Kernels and In Vitro

“…Although some of the mechanisms affecting disease resistance were previously evaluated in the pathosystems F. verticillioides-maize [25,[36][37][38] and A. flavus-maize [39][40][41], this study for the first time broadens the use of gene expression to the combined F. verticillioides-A. flavus infection, in order to better elucidate how defence gene systems can be influenced by fungal co-occurrence.…”

“…Maize samples and fungal mycelia were ground under liquid nitrogen with a pestle and mortar, and total RNA extraction and purification were carried out according to [39,40]. The amount and the quality of the total RNA was verified by fluorometric assay (Quibit, Thermo Fisher Scientific Inc. Waltham, MA, USA) as well as by agarose gel electrophoresis.…”

“…Twenty ng of single strand cDNA determined by fluorometric assay (Qubit, Thermo Fisher Scientific) were used for real-time RT-qPCR. Relative RT-qPCR was performed under the following conditions: 95 • C for 3 min and 40 cycles at 95 • C 15 s, 55-60 • C for 30 s, followed by a melting curve analysis [39,40]. Three technical replicates (within each biological replicate) were employed for each tested sample and template-free negative controls.…”

Development of early maturity maize hybrids for resistance toFusarium andAspergillus ear rots and their associated mycotoxins

“…The primary ear of 5 plants per plot was inoculated with a spore suspension of F. verticillioides MPVP 294 (Maschietto et al, 2017) and A. flavus MPVP A2092 (Lanubile et al, 2017b;Mauro et al, 2013), both originating from Italy. These strains are part of the culture collection of the Department of Sustainable Crop Production, Università Cattolica del Sacro Cuore of Piacenza, Italy.…”

Aflatoxins: biosynthesis, prevention and eradication

“…These results suggested that overexpression of maizedefence-associated genes observed in response to the atoxigenic strain could contribute to an AF reduction. The identification of genes significantly affecting the plant resistance to A. flavus or AF accumulation would accelerate the development of resistant cultivars (Lanubile et al, 2017).…”